Process of separating the constituents of mineral silicates



March 25, 1930. As. w. scoFll-:LD ET A1. 1,751,663

PROCESS OF SEPARATING THE CONSTITUENTS OF MINERAL SILICATES Oriiginal Filed May 17 1922 MEQ Dhmwwgzonv Hugs yPatented Mar. k25, 1930 N UNITED STATES PATENT OFFICE SHERMAN W. SCOIFIELD ANDY JOI-IN IB. LA RUE, OF CLEVELAND,' OHIO;V SAID LA RUE ASSIGNOR TO SAID SCOFIELD l PROCESS SEPARATING THE CONSTITUENTS O F MINERAL SILICA'IES Original application filed May '17, 1922,`Seral No. 561,704. Divided and this application vfiled February 7,

` 1924. Serial The principle of the invention is herein eX- plained, andthe best mode in which we have contemplated applying that principle, so as to distinguish it? from other inventions. The

subject matter ofV thisapplication is divided out of our `pending application Serial No. 561,704 uponfprocesses of separating the-constituents of mineral silicates;

@ur invention relates toprocesses for seplO arating the constituents of mineral silicates, and particularly to processes for extracting the potassium and other values from potash feldspar. This invention relates to improvements ina process of this general character disclosed in our pending application for U. S. Letters Patent, Serial No. `407,724, as well as the improvementsdisclosed insaid application Serial No. 561,704, from which this subject matter` has been divided out. The claims 29 of this application -arelimited to our improve-dA method of recoveringthe potassium values in two fractions for sales and for reuse, as hereinafter fully described.

The annexed drawing and the following description set forth in `detail certain .Stops embodying our invention, the-disclosedsteps; however, constituting but one of the various methods in which the principle of the said invention may be carried out. i

The drawing represents a fiow diagram of our improved process.

Ve first crush high' grade crystalline potash-feldspar to about thirty-five mesh, in orderthat a subsequent calcining 35 can be thoroughlyand economically effected. We then calcine this crushedA ore until the same is converted to an amorphous condition, in order that a subsequent vdigestion with fcaustic'potash may be effected to convert the D ore constituents into water soluble or acid 'soluble' compounds. This calcining is elicoted upon the bed of a furnace or in any other suitable manner by heating from one (l) to two (2) hours at from 800 to 1050o C. After 4 the ore has thus been reduced to an amphorous condition, we then further crush the same to abouttwo hundred (200) mesh-after which the same is digested with the caustic potash. r The digestion ofthe ore with caustic potash do is not'carried to a point where all of the ore is convertedinto water soluble potassium silicate'and potassium aluminate but there is also produced a water insoluble but an acid soluble potassiumy aluminum silicate. We use 90% caustic potashy for the alkali digestion in amount from one and one-quarter (ll/1,) to two (2) times the Weight of the ore and also an equal amount'of water, heating for from one (l) to two (2) hours at a temperature from 275 to 325 C." The operation is effected in an autoclave at a pressure of from 300 to 1350 lbs, per square inch. We then allow a further reaction period of about two (2) hours, resulting in a complete decomposition of the ore into the water or acid soluble compounds above-mentioned. By 90% caustic potash, we denote merely a certain grade of potash. It means that caustic potash' with a KOH content of ninety' (90) per cent or better should be used. In the development upon which this application is based, standard caustic potash was used for the digestion, such as Schieiilein Aor Innes- Speiden, except-where the caustic was obtained from the process itself for reuse, In buyingtfhe standard potashl for the' purpose a ninety (90) per cent grade or better was obtained. During the digestion operation con siderable hydrogen is ipormed," after the temperature has reached substantially 200 C, due to the fact that the iron walls of the autoclave are attackedby strong'fcaustic potash, the reaction being Fe|2KOH,=Fe(OK)2l`I-I2. Itmay bethat some impurity in the or'e or even in the iron acts as a catalyst for this re! action. The iro'n' later appears as an iinpur'ity in the 'aluminum salts o'r' possibly in the silica. In order that this evolved hydrogen may not form an explosive mixture with .the oxygen of the air which is inthe 7autoclave at the start, we remove this air from the autoclave during the irstpart ofthe digestion operation by allowing the pressure to reach thirty (30) to forty (40) lbs. per square inch and then allowing the oxygen to yescape from the autoclave. The already for-med steam Vdisplaces the air which escapes andiinally the interior of the autoclave contains nothingbu-t steam, indicated by a current of pure quickly condensing steam escaping from the autoclave valve.

l/Ve dilute the alkali digestion products with from one (l) to four `(4) times their volume of water and then carbonate the mixture with carbon dioxide, maintaininga pressure of about 22 inches above atmospheric pressure, the temperature being maintained at substantially `room temperature by means of a. positive removal of the generated heat. We

thus obtain the water soluble potash value in solution and precipitate aluminum hydroxide and ortho silicic acid. The mass action resulting from the pressure above-mentioned and the maintenance of normal temperature effects the carbonating in about forty-tive (45) minutes, the same taking place in two stages, the first stage resulting in a conversion of the potassium content to potassium carbonate and takingonly about five minutes and the second stage converting the potassium carbonate to bicarbonate and taking about forty (40) minutes. The reaction is basedf upon the action of the ionized acid (II-2G03) formed by the dissolving of CO2 gas in water. There is only incomplete precipitation'of the silicon and aluminum during the first stage because the potassium carbonate being strongly alkaline dissolves aluminum hydroxide and ortho silicic acid and it is not until this carbonate is very largely converted into bicarbonate, which is almost neutral in reaction, that all of the aluminum and silicon separate out. The reactions are represented, at least in principle, .by the following equations imasses ofpotassium carbonate and'potassium bicarbonate are obtained, preferably until from ,five (5) 'to ten (10) per cent of the total potassium content of the carbonate solution is removed. The potassium carbonates thus obtained also contain the sodium that is present and thus prevent the building up of the sodium content vduring repeated reuses of the causticpotash. The balance of the carbonate solution is concentrated to a 10 per cent solution which is suitable for a causticizing operation with lime to produce caustic potash for reuse and calcium carbonatev for sale. For the recovery of the aluminum and silicon values we utilize thev operations fully described, shown and claimed in the parent application Serial No. 561,704, the same constituting no part of the improvement claimed in this application.

What we claim is: Y

l. In a process of separating the constituents of mineral silicates, the steps which consist, in removing the water soluble potas- OK /OH more CO2 OH -(a) 2A1-0K 3H1CO3 z Al-OH -i- K200i 3H2C0| Al-OH KHCO \0K \`OH \OH` Potassium Carbpnic Aluminum Potassium Aluminum Potassium aluminate acid hydroxide carbonate hydroxide bicarbonate /OK /OH more CO2 OH (b) Si-OK 213500; 2 Si-OH 21h00; -l- H200; -Si-OH -I- 41111100:V

\oK on on \0K \oH \oH Potassium Carbonic Silicic Potassium Silicio Potassium silicate Vacid acid carbonate acid Of course, carbonation to formation of 100 per cent bicarbonate requires just twice the amount of CO2 that isneeded for the normal carbonate. rIhe speed of carbonation can be greatly increased by distributing the gas uniformly over the whole cross-section of the volume of liquid to obtain the most extensive contact between the gas and liquor, and also by very strong agitation. rIo the carbonation products we add about one-half (l) of their volume of water. We then repeatedly filter and wash, the wash water requirements being from two and one-quarter-(21) to four and one-half (4l/2) gallons of water perlb. of feldspar digested. These steps, of course, result in the recovery of so much of the potassium from the feldspar as was converted into bicarbonate sium value by means of caustic potash digestion and carbonation; and' then separating the soluble potassium carbonates into two fractions by evaporating the solution in steps, obtaining each time a saturated solution from which crystalline potassium carbonate and bicarbonate are obtained, until the .sodium content is removed, and then concentrating the remainder of the water soluble potassium value to a substantially ten (l0) per cent carbonate solution and causticizing.

2. In a process of lseparating the constituents of mineral silicates, the steps which consist', in removing the water soluble potassium value by means of caustic potash .digestion and treatment with carbon dioxide; and then separating the soluble potassium carbonates March-255 1930 Y F. EysMlTH 1,75L64 VALVE SEAT Filed Nov. 20, 1928 A TTORNE Y. 

